Lecture 25

Question 1

What are the two excessively simplified groups that fungi can be typed into?

Answer 1

Yeasts which are round or oval and reproduce via budding

Moulds which have tubular hyphae and reproduce via spores

Question 2

What are the two types of pathogenic yeasts?

Answer 2

Candida Albicans which is the typical cause of almost all fungal disease and cryptococcus neoformans which very rarely causes disease and is encased in a sugar capsule

Question 3

What are the three pathogenic moulds?

Answer 3

Dermatophytes that is the most common cause of mould diseases
Aspergillus species which only very rarely cause disease in patients with a very low neutrophil count
Zygomycetes

Question 4

Where is candida albicans typically found and how does it induce disease?

Answer 4

It is a commensal of the mouth, gut and vagina however overgrowth which can occur due to suppression of the immune system or its neighboring non-pathogenic bacteria

Question 5

How does canidida albicans appear in labs?

Answer 5

Black yeasts with pseudohyphae in the gram stain
Will appear as larger than bacteria
Grows well on blood agar

Question 6

What are the 4 different conditions that can occur as a result of candida albicans overgrowth?

Answer 6

Overgrowth typicaly occurs in warm moist areas
Pharyngitis via growth in the oesophagus
Vaginitis via growth in the vagina
Intertrigo via growth in the armpit
Candid vulvovaginitis or nappy rash

Question 7

Is overgrowth of candida albicans invasive?

Answer 7

No as it does not invade into tissues of the blood

Question 8

How is overgrowth of candida albicans treated?

Answer 8

Typically topical through
nystatin suspension or pastiles,
amphotericin B pastilles,
azole pessaries or cream (for vaginal infections)

Question 9

What are the two types of cryptococcus neoformans?

Answer 9

C.neoformans var neoformans which is associated with pigeon faeces
C.neoformans var gatti
associated with eucalyptus trees

Question 10

What type of disease is caused by c.neoformans?

Answer 10

Typically an asymptomatic pulmonary infection, although in severly immunocompromised patients disease can progress to meningitis

Question 11

How is meningitis caused by c.neoformans detected and then treated?

Answer 11

DIagnosis by detection of antigen, microscopy or culture

Treatment is via amphotericin B IV or oral fluconazole

Question 12

What type of disease do dermatophytes cause?

Answer 12

Tinea or ringworm which is never invasive

Question 13

What are the three dermatophytes which cause tinea?

Answer 13

Microsporum species
Trichophyton species
Epidermophyton species

Question 14

How can tinea supppurans appear to cause baldness?

Answer 14

Mould growth occurs in hair follicle, which odes not kill th hair but makes it very brittle so it easily breaks off

Question 15

What is onchomycosis?

Answer 15

Tinea of the nailbed

Question 16

How are dermatophyte infections treated?

Answer 16

A topical azole is used for most infections

Although nails require an oral azole to be used as the infection site is inaccessible

Question 17

What are two common skin infections caused by dermatophytes not including tinea?

Answer 17

Pityriasis versicolor caused by malassezia furfur, this appears as hypopigmented macules on the trunk and is treated with azoles
Seborrheic dermatitis caused by pityrosporum species which cause a greasy facial rash and dandruff these are also treated with topical azole

Question 18

What is aspergillus fumigatus?

Answer 18

A spore bearing branched mould typically found in rotting vegetation
This is a disease which only causes disease in those who are neutropenic
Can also cause allergic bronchopulmonary aspergillosis

Question 19

What is neutropenic?

Answer 19

A deficiency of neutrophils

Question 20

What is allergic bronchopulmonary aspergillosis?

Answer 20

Damage to the lungs allows build up of mucus which allows growth of aspergillus fumigatus

Question 21

What occurs with aspergillus fumigatus?

Answer 21

Cavitating pneumonia

Question 22

How is aspergillus fumigatus diagnosed?

Answer 22

Microscopy and culture

Question 23

How is aspergillus fumigatus treated?

Answer 23

Amphotericin B IV for weeks
Liposomal amphotericin B
Voriconazole and other azoles
Surgery

Question 24

How does amphotericin B function as an antifungal drug?

Answer 24

Binds to ergosterol which is not found in humans allowing disruption of targeted cytoplasmic membranes
Its infusion is rleated with anaphylatic reactions
has nephrotoxicity due to K+ loss
lipid versions (liposomal) are less topic

Question 25

What is the IV dosage of amphotericin B?

Answer 25

0.5-1g/Kg

Question 26

How do azoles function as an antifungal drug?

Answer 26

Inhibition of ergosterol synthesis

Typically given through IV and is a relatively non toxic antifungal drug